Equilibrium and kinetic studies of the folding of small globular proteins will be carried out and working models of the folding mechanism developed. Protein folding systems will be chosen which allow comparative studies of the folding reaction between proteins which differ in sequence at one or a few positions. The attempt will be made to interpret the results in terms of answers or partial answers to the following two questions: 1) What kinds of processes limit the rates of the observable kinetic steps in folding? 2) What kinds of structure or structures are formed as intermediates in the folding process?